1. Technical Field
Embodiments of the present invention generally relate to a developing device, a process cartridge, and an image forming apparatus, such as a copier, a printer, a facsimile machine, or a multifunction machine having at least two of coping, printing, facsimile transmission, plotting, and scanning capabilities, that includes a developing device.
2. Description of the Related Art
Image forming apparatuses typically include a developing device to develop latent images formed on a latent image bearer (e.g., a photoreceptor) with developer, and two-component developer consisting essentially of toner (toner particles) and magnetic carrier (carrier particles) is widely used. Developing devices of this type typically include a rotatable developer bearer inside which multiple magnetic poles are provided. For example, JP-H06-019637-A, JP-2012-189787-A, and JP-2007-248629-A propose such configurations.
In such developing devices, the developer bearer carries developer on its surface and transports the developer to a development range facing the latent image bearer, where toner in the developer is supplied to the latent image on the surface of the latent image bearer.
The developer bearer is disposed in a casing serving as a developer container to contain developer, and the surface of the developer bearer is partly exposed in the development range through an opening of the casing. Inside the casing (i.e., the developer container), while developer is circulated by one or multiple developer conveyance members, a part of circulating developer is supplied to the surface of the developer bearer. The amount of developer supplied to the developer bearer is adjusted at a position where the developer bearer faces a developer regulator, after which the developer is transported to the development range. After the toner therein is consumed in the development range, the developer leaves the surface of the developer bearer. Then, the developer is collected in the developer container and circulated together with the developer therein.
To enable high-speed output in this developing device, the velocity at which the surface of the developer bearer moves (hereinafter “surface movement velocity”) is increased. However, if the surface movement velocity is increased, it is possible that air pressure inside the developer container rises as follows.
The surface of the developer bearer moving at a high velocity causes airflow that follows the movement of the developer bearer. When the exposed surface of the developer bearer returns from the opening in the development range to inside the casing, air flows into the casing as well.
By contrast, on the surface of the developer bearer moving toward the development range, developer fills a gap (i.e., a regulation gap) between the developer regulator and the surface of the developer bearer, which inhibits air from flowing out from the opening together with the surface of the developer bearer.
In a state in which the casing is substantially filled with developer other than the opening, air pressure inside the developer container rises when air flows into the casing but does not flow out therefrom.
If air pressure rises inside the developer container, there arises a risk that toner scatters out together with air from a small clearance between the developer container and the developer bearer moving to the development range, seams of the developer container, or the like. Scattering of toner is not desirable since it causes stains on output images, contamination inside an image forming apparatus, and the like.
The patent documents listed above propose use of a pressure-release vent to discharge air from the developer container and a filter to inhibit passage of toner, thereby inhibiting toner scattering from the opening. In this configuration, pressure rise inside the developer container can be inhibited since air is released from the developer container. Accordingly, toner scattering resulting from the pressure rise inside the developer container can be suppressed.